lawyer for the Archdiocese of Boston said the church will soon begin turning over more than 50 years worth of church records, files that contain all ''credible claims'' of sexual misconduct by priests, after a state appellate judge yesterday rejected the church's bid to keep the records secret.

Appeals Court Judge Kenneth Laurence denied an appeal of a Superior Court judge's order last month that the church give lawyers for alleged victims of the Rev. Paul R. Shanley documents showing how the archdiocese handled claims against about 87 other priests, 15 of whom are now dead.

J. Owen Todd, a Boston attorney representing the archdiocese, said that Laurence suggested in his order that some documents could be deemed privileged under rules governing civil cases in state court. ''We will begin going through them and figuring out which ones are privileged,'' Todd said. ''Then we will start turning over documents.''

The text of Laurence's order is expected to be made public today.

Lawyers for the alleged victims hailed the ruling as a breakthrough that will give them a comprehensive look at the church's practices and policies on dealing with abuse.

''This is perhaps the most important ruling we've had to date,'' said Boston attorney Roderick MacLeish Jr., who represents scores of alleged victims suing the archdiocese. ''The more we can show there was a common practice of putting back into ministry priests who had credible allegations of child molestation, the harder it will be for the archdiocese to prevail in its defenses.''

Meanwhile, at a news confer1ence following Cardinal Bernard F. Law's last day of testimony in child abuse cases against Shanley, attorneys for both sides sparred over whether the appeal on the documents was a delaying tactic or a legitimate legal move by hard-pressed defense attorneys.

Before learning of the Appeals Court decision, Todd said the archdiocese was within its rights to appeal Judge Constance Sweeney's three-week order that it turn over records on the priests. Todd complained that MacLeish's demand for documents was itself a legal tactic to turn Sweeney and public opinion against the archdiocese. The sheer volume of documents requested made it difficult to comply with the judge's order quickly, Todd said.

Law yesterday was deposed for the sixth and last time in the case against Shanley. Transcripts from his testimony, which began in June, will be released 30 days from Friday, said MacLeish.

Law is still expected to testify in cases involving other priests accused of molesting children, including Joseph Birmingham and Ronald H. Paquin, MacLeish said.

Rodney Ford, father of alleged Shanley victim Gregory Ford, accused the cardinal's attorneys of displaying a ''lack or respect'' for him and his family during the depositions. Todd objected repeatedly during the testimony, he said.

Church attorneys left open the door to a settlement in a Shanley case, but MacLeish said that would not happen ''until the truth comes out'' and he had all the documents on other accused priests. Wilson Rogers Jr., Law's attorney, said he was always open to working ''towards a true and equitable settlement.''